The present invention relates to an attachment and a liquid supplying device.
An inkjet printer is widely known as a liquid jet device for jetting liquid to a target through a liquid jet head. The inkjet printer is composed of a carriage and a print head mounted on the carriage. While the carriage moves toward a printing medium as a target, ink is ejected from a nozzle formed in the print head, so that printing is performed on the printing medium.
Among these kinds of inkjet-type printing devices, one of them has such a configuration (so-called on-carriage type) that includes respective ink cartridges for supplying ink to a print head, which are mounted so as to be installed detachably on the carriage. However, ink capacity of the ink cartridge is limited in the on-carriage type of inkjet printing device. Therefore, ink cartridges need to be replaced frequently and a running cost increases, when a relatively large amount of printing is performed.
In order to solve such a problem, there is disclosed a following inkjet printer in Japanese Patent Laid-Open No. 2003-326732. In the inkjet printer disclosed in Japanese Patent Laid-open No. 2003-326732, printing is usually performed with respective ink cartridges mounted on a carriage. But, in the case where a large amount of printing is performed, attachments are mounted on a carriage to perform printing. In addition, ink is filled into the attachments mounted on the carriage from outer ink tanks through tubes and the ink is supplied to a print head due to a differential head.
However, the ink is supplied to the print head from the outer ink tank clue to a differential head in the inkjet printer, so that the supply pressure into the print head depends on the ink level within the outer ink tank. Accordingly, the weight of ink drops ejected from the print head is varied according to the ink level, so that a printing quality differs depending on the amount of ink remaining in the outer ink tank.
CN2355886 and CN2536401 disclose an automatic ink supplying device including an ink cartridge for supplying ink which is connected to a printer ink cartridge through an ink duct. Even in the automatic ink supplying devices disclosed in these Japanese Unexamined Utility Model Registration Application Publications, the ink in the ink cartridge for supplying ink provided outside the printer forms an integrated system having a constant successive pressure with the ink within the printer ink cartridge through the ink duct, so that the supply pressure into the print head depends on the ink level within the ink cartridge for supplying ink. Accordingly, there is a problem in that a printing quality is different according to the amount of ink remaining in the ink cartridge for supplying ink.
U.S. Pat. No. 5,731,319 (see Abstract) discloses a supply ink reservoir which is connected to a printing ink container of an ink cartridge through a tube device. While ink is ejected from a print head of a printing cartridge to print out a sheet, the supply ink reservoir can supply ink to the cartridge. An embodiment is disclosed in U.S. Pat. No. 5,731,319, which includes a supplement ink reservoir in which an ink container bottle is disposed in the upper portion of the supply ink reservoir. The supply ink reservoir is a part of the ink container bottle. According to the embodiment, the supplement ink reservoir and the supply ink reservoir communicate with each other through the path which is controlled by a floating valve mechanism disposed inside the supply ink reservoir. Although the liquid level of the supply ink reservoir can be controlled to be held in a substantially constant level by the floating valve mechanism, a space is required inside the supply ink reservoir so that the floating valve can operate. In addition, when the liquid level of the supply ink reservoir decreases so that the path is opened by the floating valve, the ink in the supplement ink reservoir reaches the fluid level (liquid level) of the supply ink reservoir through the space. Therefore, a minute pressure variation or pressure pulse acts on the ink to be supplied to the printing cartridge, which makes it possible to reduce a printing quality.
U.S. Pat. No. 5,367,328 (see lines 3 to 25 and lines 56 to 59 in the tenth column) discloses following embodiments. One embodiment uses a passive differential pressure in sending ink to an ink supply container from an ink reservoir container 14, in an integrated system without mechanical assistance from a pump or the like. Another embodiment is an active embodiment which delivers ink to an inkjet cartridge from an outer ink reservoir container through a mechanical pump or the like in place of the passive differential pressure. In addition, U.S. Pat. No. 5,367,328 discloses an embodiment which uses a capillary action of a form element in order to generate the differential pressure between an upper opening vent portion of the ink supply container which is connected to the ink reservoir container operatably and a lower portion close to a print head of the ink supply container, in which a bottom of the ink reservoir container has the substantially same level as that of the ink supply container. Since the pump or the like needs to be mounted and controlled in an active system, the entire system becomes complicated. When the form element is disposed in the ink supply container in a passive system, the ink flow within the form element needs to be optimal.
The present invention has been made to solve the above-mentioned problems. An advantage of the present invention is that it provides an attachment and a liquid supplying device capable of securing a constant weight of ejected liquid drops of a liquid jet head, regardless of the amount of liquid consumed in an outer liquid container.